The present invention relates to an optical disc such as so-called CD-R or so-called CD-RW (CD-Rewritable), on which data can be recorded, and to an apparatus and method for recording data on the optical disc.
An optical disc is a disc-shaped recording medium that has a signal-recording layer. When a light beam is applied to the signal-recording layer, data signals are recorded on the disc or reproduced therefrom. (Hereinafter, the operation of recording data on or reproducing data from the disc will be referred to as xe2x80x9crecording/reproducing.xe2x80x9d)
Among such optical discs are playback-only discs, each comprising a substrate on which data signals have been recorded in the form of pits. Examples of playback-only discs are CD (Compact Disc) and CD-ROM (CD-Read Only Memory). In the case of a playback-only disc, the major surface of the substrate, in which the trains of pits are formed, functions as the signal-recording layer.
There is a demand for an optical disc on which new data can be written or the data can be rewritten. To meet the demand, a new type of an optical disc has been developed, which may be used in the so-called compact disc recorder system and on which additional data signals can be recorded. (Hereinafter, the compact disc of this type will be referred to as xe2x80x9cCD-R.xe2x80x9d) The CD-R has a signal-recording layer on which data signals can be recorded. The signal-recording layer is made of material the major component of which is an organic dye. When a light beam is applied to the signal-recording layer, the reflectance of the layer changes at the part irradiated with the light beam. A data signal is thereby recorded on the disc. The reflectance of that part of the layer is detected, thereby reproducing the data signal.
Another type of an optical disc on which data can be recorded is, for example, a CD-RW (CD-Rewritable). The CD-RW is a phase-change optical disc, on which data can be rewritten by using the phase changes in the signal-recording layer.
The CD-R and CD-RW each have a] lead-in area. The lead-in area includes an area called xe2x80x9cPCA (Power Calibration Area), which is used to adjust the power for the data-recording beam.
The PCA consists of two types of areas, i.e., test area and count area. Signals are recorded in test area, and the asymmetry of the signals recorded is measured to find the optimal power for the data-recording beam.
The test area and the count area take one-to one relation. In the case of the conventional CD-R or CD-RW of the single-density CD format, the PCA consists of 100 test areas and 100 count areas. Each test area is paired with one count area.
In recent years, the amount of data processed in, for example, personal computers has been increasing. It is desired that CD-Rs and CD-RWs used as recording media for recording such data should have a large storage capacity.
In an optical disc having such a large storage capacity, the number of times the power can be adjusted may be insufficient if the PCA consists of only 100 test areas and only 100 count areas. Hence, the amount of data that can be recorded on the optical disc may be limited.
The present invention has been made in view of the foregoing. An object of the invention is to provide an optical disc in which the power can be adjusted a sufficient number of times and the storage capacity of which can be increased. Another object of the invention is to provide a data-recording apparatus and data-recording method, either using the optical disc.
To achieve the first object of the invention, an optical disc according to the invention has a power calibration area for calibrating the power of a data-recording laser beam. The power calibration area is provided at an inner peripheral part of the disc and has test areas and count areas. The test areas are provided to accomplish trial writing of data. The count areas are provided to record data representing the use condition of the test areas, and the number of the test areas is increased in accordance with an increase in the recording density and storage capacity of the optical disc.
The optical disc may be CD-formatted and may have a recording density about twice as high as that of an optical disc of the existing CD format (e.g., single-density CD-R). The optical disc may have 800 to 1200 test areas that are provided in the power calibration area.
A data recording apparatus according to the invention is designed to record data on an optical disc by calibrating the power of a data-recording laser beam. The optical disc has a calibration area which is provided at an inner peripheral part of the disc and which has test areas and count areas. The test areas are provided to accomplish trial writing of data. The count areas are provided to record data representing the use condition of the test areas. The number of the test areas is increased in accordance with an increase in the recording density and storage capacity of the optical disc.
Since the number of the test areas is increased in proportion to the recording density and storage capacity of the optical disc, the power of the data-recording laser beam can be adjusted many times. Therefore, the amount of data that may be recorded on the optical disc is not limited at all.
Moreover, the size of the test areas may be reduced to, for example, one equivalent to two ATIP information frames recorded in a pregroove made in one surface of the disc. In this case, the disc can have sufficiently large data regions.
A data recording method according to this invention is designed to record data on an optical disc by calibrating the power of a data-recording laser beam. The optical disc has a calibration area provided at an inner peripheral part of the disc. The calibration area has test areas for accomplishing trial writing of data and count areas for recording data representing the use condition of the test areas. The number of the test areas is increased in accordance with an increase in the recording density of the optical disc.
In the method, the number of the test areas is increased in proportion to the recording density and storage capacity of the optical disc. The power of the data-recording laser beam can be therefore adjusted many times. As a result, the amount of data that may be recorded on the optical disc is not limited at all.
In addition, the size of the test areas may be reduced to, for example, one equivalent to two ATIP frames recorded in a pregroove made in one surface of the disc. Thus, the disc can have sufficiently large data regions.
As seen from the above, the number of test areas provided on the disc is increased in proportion to the increase in the storage capacity of the disc. This makes it possible to adjust the power of the data-recording laser beam as many times as desired. Thus, the amount of data that may be recorded on the optical disc is not limited at all.
Moreover, the test areas provided on the disc have the smallest possible size (e.g., the size equivalent to two ATIP frames recorded in the pregroove), and the count areas are provided on the disc in the smallest possible number. Therefore, the disc can have sufficiently large data regions.